Socialization begins with the child's first contact with the environment. Thus, it starts in the family home where children acquire basic social skills. Every child has different social skills based on their temperament, personality traits and parenting styles. Apart from family home, schools are one of most important agents of socialization. In schools children are in contact with new people which impact not only their behaviour and attitude but also school success. One of most important social contacts in the schools are those with classroom peers. Social interactions with peers are good predictor of school success and therefore they can affect educational achievement. It was found that peer acceptance and rejection affect school success and involvement in school activities. Specifically, students who are popular and accepted by classmates achieve better school performance, while on the other hand, students with unpopular sociometric status achieve poorer school performance. Also, peer rejection is associated with low interest in school activities, dropping out of school, poor performance and juvenile delinquency.